1. Field of the Invention
The present invention relates to an ex-core nuclear instrumentation system that monitors neutron flux outside a reactor vessel and, more particularly, relates to an ex-core nuclear instrumentation panel that constitutes the ex-core nuclear instrumentation system.
2. Description of the Related Art
An ex-core nuclear instrumentation system continuously monitors a neutron flux outside a reactor vessel of a pressurized water reactor (PWR) and accordingly the state of the reactor at start and in operation is monitored; and when an abnormality is detected in the condition of the neutron flux, the ex-core nuclear instrumentation system outputs an alarm signal and a signal for emergency shutdown of the reactor and accordingly the reactor is protected. The ex-core nuclear instrumentation system mainly includes a neutron detector that measures the neutron flux and converts the neutron flux into a current value and an ex-core nuclear instrumentation panel that performs arithmetic processing of the converted current value to convert into the signals.
Generally, a neutron measurement range of the ex-core nuclear instrumentation system is divided into a neutron source range, an intermediate range, and an output range (operation range) depending on the level of neutron flux from a stopped state to output operation of the reactor. The structure and function of the neutron detector and the ex-core nuclear instrumentation panel is different for each range, and a detector signal processing circuit (I/E amplifier, that is, current/voltage amplifier) is used for performing arithmetic processing of the output range.
An ex-core nuclear instrumentation system includes a neutron detector and an ex-core nuclear instrumentation panel as above-mentioned. A plurality of the neutron detector is located around outside a reactor vessel to be provided inside a reactor containment vessel. The neutron detector measures neutron flux leaked from the reactor vessel and converts the neutron flux into a current value. The current value is inputted to a detector signal processing circuit of the ex-core nuclear instrumentation panel and is converted into an output voltage corresponding to a reactor power level. Then, the output voltage of the detector signal processing circuit is inputted to a signal processing card. The signal processing card performs analog/digital (A/D) conversion and engineering value conversion, and outputs various signals to an operation panel and an input and output card in a reactor protection based system. Further, the measured data which is converted into digital data is stored in an electrically rewritable storage device such as EEPROM (Electronically Erasable and Programmable Read Only Memory) (registered trademark).
Here, in order to correct the aged deterioration of a neutron detector itself, an amplifier of a detector signal processing circuit, etc., calibration work is required (For example, Japanese Unexamined Patent Publication No. 2000-266884). The calibration work is performed via an operation panel by an operator. In performing the calibration work, in some cases, work of rewriting the data stored in the storage device is generated.
Regarding conventional ex-core nuclear instrumentation systems, FIG. 4 is a block diagram showing an example of a memory access structure for rewriting the data which is stored in a storage device. The memory access structure includes a signal processing card 111, on which a CPU 220, a FPGA (Field Programmable Gate Array) 230 and an electrically rewritable nonvolatile memory 240 such as an EEPROM (registered trademark) are equipped, and an operation panel 120 which is operated by a human being from outside. The operation panel 120 is provided at an electronic substrate 310 which is separated from the signal processing card 111.
The CPU 220 mainly performs control of signal processing or performs arithmetic processing. The data is inputted from the operation panel 120 by communicating with the FPGA230. When the data is inputted, a write signal which is transmitted from the CPU is processed by a software with FPGA 230, and the FPGA230 directly rewrites the data which is stored in the nonvolatile memory 240.